Systems for manufacturing downhole tools and downhole tool parts

ABSTRACT

Methods, systems and compositions for manufacturing downhole tools and downhole tool parts for drilling subterranean material are disclosed. A model having an external peripheral shape of a downhole tool or tool part is fabricated. Mold material is applied to the external periphery of the model. The mold material is permitted to harden to form a mold about the model. The model is eliminated and a composite matrix material is cast within the mold to form a finished downhole tool or tool part.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/479,534, filed Jun. 5, 2009, now U.S. Pat. No. 8,201,610, issued Jun.19, 2012, and is related to the subject matter of U.S. patentapplication Ser. No. 13/158,368, filed Jun. 10, 2011, now U.S. Pat. No.8,317,893, issued Nov. 27, 2012, which is a divisional of U.S. patentapplication Ser. No. 12/479,534, filed Jun. 5, 2009, now U.S. Pat. No.8,201,610, issued Jun. 19, 2012; U.S. patent application Ser. No.12/192,292, filed Aug. 15, 2008, now U.S. Pat. No. 8,172,914, issued May8, 2012, which is a divisional of U.S. patent application Ser. No.10/848,437, filed May 18, 2004, now abandoned; U.S. patent applicationSer. No. 12/763,968, filed Apr. 20, 2010, now U.S. Pat. No. 8,087,324,issued Jan. 3, 2012, which is a continuation of U.S. patent applicationSer. No. 11/116,752, filed Apr. 28, 2005, now U.S. Pat. No. 7,954,569,issued Jun. 7, 2011, which application is a continuation-in-part of U.S.patent application Ser. No. 10/848,437, filed May 18, 2004, nowabandoned; U.S. patent application Ser. No. 12/033,960, filed Feb. 20,2008, now U.S. Pat. No. 8,007,714, issued Aug. 30, 2011, which is adivisional of U.S. patent application Ser. No. 11/116,752, filed Apr.28, 2005, now U.S. Pat. No. 7,954,569, issued Jun. 7, 2011, which is acontinuation-in-part of U.S. patent application Ser. No. 10/848,437,filed May 18, 2004, now abandoned; U.S. patent application Ser. No.11/932,027, filed Oct. 31, 2007, now abandoned, which is a continuationof U.S. patent application Ser. No. 11/116,752, filed Apr. 28, 2005, nowU.S. Pat. No. 7,954,569, issued Jun. 7, 2011, which is acontinuation-in-part of U.S. patent application Ser. No. 10/848,437,filed May 18, 2004, now abandoned; U.S. patent application Ser. No.13/111,666, filed May 19, 2011, pending; U.S. patent application Ser.No. 13/111,739, filed May 19, 2011, pending; and U.S. patent applicationSer. No. 13/111,783, filed May 19, 2011, pending.

FIELD OF TECHNOLOGY

The present application is directed to methods, systems and compositionsfor manufacturing downhole tools and downhole tool parts havingincreased wear resistance, strength and toughness.

BACKGROUND

Downhole tools and tool parts including roller cone bits and fixedcutter drag bits are machined from steel or fabricated by infiltrating abed of hard particles, such as cast carbide and/or sintered cementedcarbide with a binder, such as a copper-base alloy.

Steel bodied bits are typically fabricated from a round stock or a blankmachined to a desired geometry including external and internal featuresof the bit body. Hard-facing techniques may be used to applywear-resistant materials to the face of the bit body and other criticalareas of the surface of the bit body.

Conventional metal particulate-based infiltration involves placing a bedof hard particles within a mold and consolidating the bed to the desireddensity. The consolidated bed of hard particles is infiltrated with amolten binder which solidifies to form a solid bit body including adiscontinuous phase of hard particles within a continuous phase ofbinder.

Cutting elements or inserts are fixed to the fabricated bit body withinpockets at predetermined positions to optimize the rate of penetrationinto a subterranean formation. Cutting elements or inserts are securedto the pockets within the bit body by brazing, welding, adhesivebonding, or mechanical pressing after the bit body is fabricated.

Improved methods, systems and compositions for manufacturing downholetools and tool parts having increased wear resistance, strength andtoughness are herein disclosed.

SUMMARY

Methods, systems and compositions for manufacturing downhole tools anddownhole tool parts for drilling subterranean material are disclosed. Amodel having an external peripheral shape of a downhole tool or toolpart is fabricated. Mold material is applied to the external peripheryof the model. The mold material is permitted to harden to form a moldabout the model. The model is eliminated and a composite matrix materialis cast within the mold to form a finished downhole tool or tool part.

The foregoing and other objects, features and advantages of the presentdisclosure will become more readily apparent from the following detaileddescription of exemplary embodiments as disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present application will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 is an inverted perspective view of an exemplary three dimensionalfixed cutter bit body model according to one embodiment;

FIGS. 2A through 2C illustrate an exemplary system and method forfabricating a bit body mold from a bit body model according to oneembodiment;

FIG. 3 is an inverted perspective view of an exemplary three dimensionalfixed cutter bit body model including bit body elements according toanother embodiment;

FIG. 4A through 4C illustrate an exemplary system and method forfabricating a bit body mold from a bit body model and casting acomposite matrix material within the mold according to one embodiment;

FIGS. 5A through 5C illustrate an exemplary system and method forcasting a composite matrix material within a bit body mold according toanother embodiment;

FIGS. 6A through 6E illustrate exemplary systems and methods forfabricating a roller cone mold from a roller cone model and casting acomposite matrix material within the mold according to one embodiment;

FIG. 7 illustrates a phase diagram of an exemplary composite matrixmaterial for casting downhole tools and tools parts in accordance withthe present disclosure; and

FIGS. 8A through 8D illustrate microstructures formed from casting acomposite matrix material in accordance with the present disclosure.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where considered appropriate, reference numerals may be repeated amongthe figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the example embodiments described herein.However, it will be understood by those of ordinary skill in the artthat the example embodiments described herein may be practiced withoutthese specific details. In other instances, methods, procedures andcomponents have not been described in detail so as not to obscure theembodiments described herein. Downhole tools such as roller cone bits,fixed cutter drag bits, casing bits, reamers, bi-center rotary drillbits, reamer wings, down-hole milling tools, bi-center drill bits, wellcompletion equipment and/or other drilling tools known in the art fordrilling subterranean material and completing subterranean wells may bemanufactured using systems and methods disclosed herein. As used herein,the term “downhole tool” encompasses any and all such apparatuses andcomponent parts thereof.

FIG. 1 is an inverted perspective view of an exemplary three dimensionalfixed cutter bit body model 12 according to one embodiment. The bit bodymodel 12 may be fabricated using three-dimensional modeling systems andlayered manufacturing processes including, but not limited to, selectivelaser sintering (SLS), stereolithography (STL), three-dimensionalprinting, laminated object manufacturing (LOM) or any other rapidprototyping method for producing a three-dimensional bit body model 12such as those disclosed in U.S. Pat. No. 6,200,514 incorporated hereinby reference. The bit body model 12 may also be fabricated by hand.

The bit body model 12 may be constructed from material such as wax,polymer or combinations thereof. The bit body model 12 includes aplurality of longitudinally extending blades 18 that define a pluralityof adjacent junk slots 30 thereinbetween. Cutter pockets 22 for securingcutting elements are formed in the bit body model 12 along the leadingperipheral edge 27 of each blade 18 proximate the distal end 20 of thebit body model 12. A plurality of rows of cutter pockets 22 may beprovided to secure a plurality of rows of cutting elements. Cutterpockets 22 may also include inclined buttresses 24 to support cuttingelements from the rear. Nozzle cavities 38 for securing nozzles areformed in the bit body model 12 within the junk slots 30. Gage pads 28are positioned at the external periphery of the bit body model 12longitudinally adjacent to each blade 18. Gage trimmer pockets 26 forsecuring gage trimmers are formed in the bit body model 12 immediatelyadjacent and above the gage pads 28. The bit body model 12 may be usedto fabricate a fixed cutter bit body mold.

FIGS. 2A through 2C illustrate an exemplary system and method forfabricating a bit body mold 410 from a bit body model 12 according toone embodiment. Preferably, mold material 412 will not substantiallydegrade the bit body model 12. To ensure proper removal of the bit bodymodel 12 from the mold 410, the mold material 412 is selected to hardenat a temperature lower than the melting temperature of bit body model 12(e.g. 100° C.). The external periphery of the bit body model 12 may becoated with a mold release material that resists adherence to the moldmaterial 412. Mold release material may comprise tetra-fluoroethylene,waxy materials or oils that facilitate removal of the bit body model 12from a hardened mold 410. Mold material 412 may comprise ceramic, sand,graphite, clay, plastic, rubber, wax, refractory material and/or othermaterial known in the art for fabricating downhole tool molds.

In an example embodiment, at least one first internal layer of zirconiumsilicate (ZrSiO4) mold material 412 is applied to the external peripheryof bit body model 12 to assure a proper surface finish of the mold 410.Additional layers of mold material 412 including, but not limited to,ceramic, sand, graphite, clay, plastic, rubber, wax or refractorymaterial may be applied on top of at least one layer of zirconiumsilicate (ZrSiO4) to finish and strengthen the mold 410 for handling.

Preferably, a base 15 of the bit body model 12 remains exposed throughthe mold material 412 during application of the mold material 412 to theexternal periphery of the bit body model 12. A base 15 or other portionof the bit body model 12 may also be exposed through the mold 410 tocreate an opening 414 (shown in FIG. 2C) after the mold 410 hashardened.

Referring to FIG. 2B, displacement materials, mold inserts and/orperforms 408 made from consolidated sand, graphite, or other material,may be disposed within an internal cavity 13 of bit body model 12 toprovide support, prevent collapse and prevent distortion of the bit bodymodel 12 during application of the mold material 412 to the externalperiphery of bit body model 12. Preforms 408 may also be used to createprotrusions that define the exterior geometry of the bit body model 12.

Referring to FIG. 2A, mold material 412 may be applied to bit body model12 in several ways, including but not limited to, submerging the bitbody model 12 in a slurry of mold material 412, spraying a quantity ofmold material 412 on the external periphery of the bit body model 12,placing the bit body model 12 into a container and pouring mold material412 around the bit body model 12, applying mold material 412 in slurryor paste form to the external periphery of the bit body model 12 orblowing mold material 412 in slurry or paste form on the externalperiphery of the bit body model 12.

Mold material 412 may be applied to the bit body model 12 in a pluralityof thin layers. Prior to application of each layer of mold material 412,the previous layer may be permitted to cure or substantially harden. Thebit body model 12 may also be submerged in a slurry of mold material 412a plurality of times. Prior to each submersion, the previous layer ofmold material 412 may be permitted to cure or substantially harden. Moldmaterial 412 may be cured or substantially hardened at ambienttemperature or at an increased temperature that will not melt or degradethe bit body model 12. Curing may be facilitated with an air blower orby baking the mold 410 in an oven.

It is also contemplated that bit body elements such as cutting elements,nozzles, gage trimmers, bearing elements, cutting control structures orother bit body elements known in the art may be positioned within themold 410 before the mold material 412 cures or substantially hardens.After bit body elements are positioned within the mold 410, the mold 410may be fully cured. During casting of the downhole tool or tool part,described in further detail below, a composite matrix material is castinto the mold 410 and about a portion of the bit body elements to form ametallurgical bond between the composite matrix material and the bitbody elements.

Referring to FIG. 2C, once the mold material 412 has cured orsufficiently hardened, the bit body model 12 is removed from the mold410, through an opening 414 of the mold 410. If the bit body model 12 issufficiently hollow, it may be collapsed to facilitate removal from themold 410. The bit body model 12 may then be used to produce another mold410.

FIG. 3 is an inverted perspective view of an exemplary three dimensionalfixed cutter bit body model 12 including bit body elements according toanother embodiment. Bit body elements, including but not limited to,cutting elements 22′, nozzles 36, gage trimmers 26′, bearing elements42, cutting control structures 31 and other bit body elements know inthe art may be positioned at the external periphery of the bit bodymodel 12 before mold material is applied. Cutting elements 22′ arepositioned at the external periphery of the bit body model 12 along theleading peripheral edge 27 of each blade 18 proximate the distal end 20of the bit body model 12. A plurality of rows of cutting elements 22′may be positioned along the leading peripheral edge 27 of each blade 18proximate the distal end 20 of the bit body model 12. Nozzles 36 arepositioned at the external periphery of the bit body model 12 within thejunk slots 30. Gage trimmers 26′ are positioned at the externalperiphery of the bit body model 12 immediately adjacent and above thegage pads 28. Bearing elements 42 are positioned at the externalperiphery of the bit body model 12 on the blades 18. Cutting controlstructures 31 including splitters, breakers, diverters and/or wedges maybe positioned at the external periphery of the bit body model 12proximate the cutting elements 22′ and along the leading side wall 46 ofthe junk slots 30. The bit body model 12 including bit body elements maybe used to fabricate a bit body mold.

FIG. 4A through 4C illustrate an exemplary system and method forfabricating a bit body mold 410 from a bit body model 12 and casting acomposite matrix material within the mold 410 according to oneembodiment. The bit body model 12 may be fabricated usingthree-dimensional modeling systems and layered manufacturing processesherein disclosed. The bit body model 12 may also be fabricated by hand.The bit body model 12 may be constructed from material such as wax,polymer or combinations thereof. A down sprue 52 and sprue cup 54 aresecured to the bit body model 12 to create a mold assembly 56. The downsprue 52 and sprue cup 54 may be constructed from material such as wax,polymer or combinations thereof. The down sprue 52 and sprue cup 54 maybe constructed from the same material as the bit body model 12 or adissimilar material.

Bit body elements 460 including, but not limited to, cutting elements,nozzles, gage trimmers, bearing elements and cutting control structuresmay be positioned at the external periphery of the bit body model 12before mold material 412 is applied to the bit body model 12 and atleast a portion of the bit body elements 460. Bit body elements 460 maybe manufactured from one or more materials, including but not limitedto, monotungsten carbide (WC), ditungsten carbide (W₂C),macro-crystalline tungsten carbide, cobalt, titanium carbide, tantalumcarbide, metal borides, metal oxides, metal nitrides, polycrystallinediamond compact (PDC), thermally stable polycrystalline diamond (TSP),cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN),tungsten, iron, nickel, titanium and boron carbide.

Mold material 412 may be applied to the mold assembly 56 by submergingthe mold assembly 56 in a flask 50 containing mold material 412. Moldmaterial 412 may comprise ceramic, sand, graphite, clay, plastic,rubber, wax and/or other refractory materials known in the art forfabricating downhole tool molds.

In an example embodiment, the mold material 412 is a ceramic slurrycomprising zirconium silicate (ZrSiO4), water and alcohol. The moldassembly 56 may be submerged in the mold material 412 a plurality oftimes. Prior to each submersion, the previous layer of mold material 412may be permitted to cure or substantially harden. Mold material 412 maybe cured or substantially hardened at ambient temperature or at anincreased temperature. Curing may be facilitated with an air blower orby baking the resulting mold 410 in an oven.

In an example embodiment, at least one first internal layer of ceramicslurry mold material 412 is applied to the external periphery of the bitbody model 12 to assure a proper surface finish of the mold 410.Additional layers of mold material 412 including, but not limited to,ceramic, sand, graphite, clay, plastic, rubber, wax or refractorymaterial may be applied on top of at least one layer of ceramic slurrymold material 412 to finish and strengthen the mold 410 for handling.

Mold material 412 may be applied to external periphery of the moldassembly 56 in several ways, including but not limited to, spraying moldmaterial 412 on the external periphery of the mold assembly 56, placingthe mold assembly 56 into a container and pouring mold material 412 onthe external periphery of the mold assembly 56, applying mold material412 to the external periphery of the mold assembly 56 in paste form, orblowing mold material 412 on the external periphery of the mold assembly56.

After a sufficient quantity of mold material 412 (e.g. ½″ layer of moldmaterial) is applied to the external periphery of the mold assembly 56including the down sprue 52, the sprue cup 54 and the bit body model 12,the mold material 412 and mold assembly 56 is heated to a temperaturesufficient to cure or substantially harden the mold material 412 andmelt, burn and/or vaporize the mold assembly 56 from within the mold410. The bit body elements 460 are retained within the mold 410 (shownin FIG. 4B) after the mold assembly 56 (shown in FIG. 4A) is melted,burned and/or vaporized from within the mold 410. The mold assembly 56may also be dissolved with a dissolving composition.

Referring to 4C, after the mold assembly 56 (shown in FIG. 4A) ismelted, burned vaporized or dissolved from within the mold 410, theremaining structure includes the mold 410, a down sprue 52′ and spruecup 54′ formed from mold material. A composite matrix material in powderform may be placed within the sprue cup 54′, the down sprue 52′ and themold 410. The composite matrix material is heated to a temperaturesufficient to melt the composite matrix material. The composite matrixmaterial flows down the down sprue 52′ and into the mold 410. Thecomposite matrix material hardens within the mold 410 to form ametallurgical bond with the bit body elements 460 (shown in FIG. 4B).The mold 410 may be removed from the cast hardened composite matrixmaterial to produce a finished fixed cutter drill bit body.

The composite matrix material may be cast within the mold 410 undervacuum conditions in a vacuum furnace. The composite matrix material maybe also cast within the mold 410 in the presence of a protectiveatmosphere such as an inert atmosphere including argon or a reducingatmosphere including hydrogen, methane and/or other gaseous hydrocarbonsthat scavenge oxygen. It is also contemplated that the composite matrixmaterial may be cast within the mold 410 in air after applying aprotective coating over the composite matrix material. The protectivecoating may comprise silicon oxide, boron oxide, calcium oxide or zincoxide.

FIGS. 5A through 5C illustrate an exemplary system and method forcasting a composite matrix material within a bit body mold 410 accordingto another embodiment. Bit body elements 460, including but not limitedto, cutting elements, nozzles, gage trimmers, bearing elements, cuttingcontrol structures and/or other bit body elements known in the art areretained within a fixed cutter bit body mold 410 after a bit body modelis melted, burned vaporized or dissolved from within the mold 410. Thebit body mold 410 is used to manufacture a fixed cutter bit body 12′ bycasting a composite matrix material 422 within the bit body mold 410 andover at least a portion of the bit body elements 460. It is alsocontemplated that bit body elements 460 may be positioned directlywithin the mold 410 before the mold 410 is permitted to fully cure andafter the bit body model is melted, burned vaporized or dissolved.

Bit body elements 460 including cutting elements, nozzles, gagetrimmers, bearing elements, cutting control structures and/or other bitbody elements known in the art may be fabricated from one or morematerials, including but not limited to, monotungsten carbide (WC),ditungsten carbide (W₂C), macro-crystalline tungsten carbide, cobalt,titanium carbide, tantalum carbide, metal borides, metal oxides, metalnitrides, polycrystalline diamond compact (PDC), thermally stablepolycrystalline diamond (TSP), cubic boron nitride (CBN),polycrystalline cubic boron nitride (PCBN), tungsten, iron, nickel,titanium and boron carbide.

In an example embodiment, bit body elements 460 are fabricated fromsintered tungsten carbide (tungsten carbide and cobalt). To assureadequate wear resistance of the sintered tungsten carbide bit bodyelements 460, the cobalt content is less than 20 weight percent. Afterthe composite matrix material 422 is cast and permitted to harden, ametallurgical bond is formed between the composite matrix material 422and the sintered tungsten carbide bit body elements 460. The sinteredtungsten carbide bit body elements 460 retain their mechanicalproperties within the finished drill bit body 12′.

During casting, the mold 410 may be disposed in a support structure, amold casing or a pliable vessel filled with support material such assand to prevent damage to the mold 410 and composite matrix materialcast therein. Mold inserts 418 that define the external geometry of thebit body 12′ may be inserted through an opening 414 and arranged in thecavity 416 of the mold 410 to support the mold 410 during casting.

A composite matrix material 422 comprising two or more constituents thatform a single miscible liquid mixture of all constituents at or abovethe eutectic temperature of the composite matrix material is cast withinthe mold 410. The composite matrix material 422 may be poured in liquidor molten form into the cavity 416 of the mold 410 from any suitablecontainer 440 such as a crucible or ladle that will not degrade duringcasting. The composite matrix material 422 may comprise two or moreconstituents including, but not limited to, monotungsten carbide (WC),ditungsten carbide (W₂C), cobalt, tungsten, iron, nickel, titanium andboron carbide. The mold 410 is removed from the cast hardened compositematrix material 422 to produce a finished drill bit body 12′.

FIG. 7 illustrates a phase diagram of an exemplary composite matrixmaterial for casting downhole tools and tools parts in accordance withthe present disclosure. The composite matrix material comprisesmonotungsten carbide and cobalt. The X-axis of the phase diagramrepresents the relative concentrations of monotungsten carbide andcobalt in terms of the monotungsten carbide atomic percent. The Y-axisrepresents the temperature of the composite matrix material in terms ofCelsius. The eutectic point represents the minimum melting temperatureof the composite matrix material and is the point at which a singlemiscible liquid phase (A) comprising a mixture of monotungsten carbideand cobalt is formed. L represents a multi-component liquid phase, βrepresents a solid phase of tungsten, WC represents a solid phase oftungsten carbide and η represents a ternary phase of Co₃W₃C. Theeutectic temperature of the composite matrix material is about 1357° C.The eutectic point is depicted on the phase diagram at a monotungstencarbide content of about 25 atomic percent (cobalt content of about 75atomic percent) and a temperature of about 1357° C.

It is advantageous to cast the downhole tool or tool part with thecomposite matrix material in the liquid phase (A) when a single miscibleliquid mixture of monotungsten carbide and cobalt is formed. Liquidphase (A) casting assures that the composite matrix material flows tothe edge of the mold resulting in a downhole tool or tool part with fulland uniform density. Casting the downhole tool or tool part with acomposite matrix material at or near the eutectic compositionfacilitates liquid phase (A) casting at lower processing temperatures(e.g. 1357° C. to 1500° C.) without the need for melting pointdepressing additives.

As illustrated in the phase diagram, the composite matrix material is inthe liquid phase (A) at relatively low processing temperatures (e.g.between about 1357° C. and 1500° C.) when the cobalt content of thecomposite matrix material is equal to or greater than about 70 atomicpercent. Once the composite matrix material hardens, the monotungstencarbide (WC) and cobalt separate into individual constituents to form acontinuous cobalt phase and a particulate phase of monotungsten carbide(WC) grains dispersed throughout.

Referring to FIGS. 5A through 5C, a composite matrix material 422comprising monotungsten carbide (WC) and cobalt may be cast in molten orliquid form within the cavity 416 of the mold 410 and over at least aportion of the bit body elements 460 retained within the mold 410. Moldinserts 418 that define the external geometry of the bit body 12′ may beinserted through an opening 414 and arranged in the cavity 416 of themold 410 to support the mold 410 during casting. The composite matrixmaterial 422 may be poured into the cavity 416 of the mold 410 and overa portion of the bit body elements 460 from a container 440 such as acrucible or ladle that will not degrade during casting. The compositematrix material 422 may be cast at the eutectic composition to achieveliquid phase casting at the lowest melting temperature of the compositematrix material 422. The composite matrix material may also be superheated to a temperature substantially above the eutectic temperature todecrease the viscosity of the composite matrix material 422 and toassure that the composite matrix material 422 remains in the liquidphase to cover all surfaces of the mold 410 during casting.

The composite matrix material 422 may be cast within the cavity 416 ofthe mold 410 under vacuum conditions in a vacuum furnace. The compositematrix material 422 may be cast within the cavity 416 of the mold 410 inthe presence of a protective atmosphere such as an inert atmosphereincluding argon or a reducing atmosphere including hydrogen, methaneand/or other gaseous hydrocarbons that scavenge oxygen. It is alsocontemplated that the composite matrix material 422 may be cast withinthe cavity 416 of the mold 410 in air after applying a protectivecoating over the composite matrix material. The protective coating maycomprise silicon oxide, boron oxide, calcium oxide or zinc oxide. Thecomposite matrix material 422 may be permitted to harden at ambienttemperature, at an increased temperature, in open air or in a protectiveatmosphere. Once the composite matrix material 422 hardens, the mold 410may be removed from the cast hardened composite matrix material 422 toproduce a finished drill bit body 12′.

Referring to FIG. 5C, a particulate material 424 may be selectivelydispersed within the mold cavity 416. The composite matrix material 422is infiltration cast into the selectively dispersed particulate material424 within the mold cavity 416 to increase the strength, wear resistanceor toughness of select surfaces of the finished bit body 12′ (shown inFIG. 5B). Particulate material 424 may comprise one or moreconstituents, including but not limited to, monotungsten carbide (WC),ditungsten carbide (W₂C), macro-crystalline tungsten carbide, cobalt,titanium carbide, tantalum carbide, metal borides, metal oxides, metalnitrides, polycrystalline diamond compact (PDC), thermally stablepolycrystalline diamond (TSP), cubic boron nitride (CBN),polycrystalline cubic boron nitride (PCBN), tungsten, iron, nickel,titanium and boron carbide.

The particulate material 424 may be evenly dispersed throughout thecavity 416 of the mold 410 before the composite matrix material 422 isinfiltration cast within the cavity 416. More than one bed ofparticulate material 424 comprising one or more dissimilar constituentsmay also be dispersed throughout the cavity 416 of the mold 410 beforethe composite matrix material 422 is infiltration cast within the cavity416. The strength, wear resistance or toughness of select surfaces ofthe finished bit body 12′ may be optimized by varying the compositionand location of the particulate material 424 within the cavity 416 ofthe mold 410.

In an example embodiment, the particulate material 424 comprisestungsten carbide and cobalt. The cobalt content of the particulatematerial 424 is less than 20 weight percent to assure sufficient wearresistance of select surfaces of the finished bit body 12′ (shown inFIG. 5B).

FIGS. 6A through 6E illustrate exemplary systems and methods forfabricating a roller cone mold 210 from a roller cone model 200 andcasting a composite matrix material within the mold 210 according to oneembodiment. Referring to FIG. 6A, a cross sectional view of an exemplarythree dimensional roller cone model 200 is illustrated. The roller conemodel 200 may be fabricated by using three-dimensional modeling systemsand layered manufacturing processes herein disclosed. The roller conemodel 200 may also be fabricated by hand. A plurality of cutting inserts252 may be positioned at the external periphery of the roller cone model200. The cutting inserts 252 may be fabricated from one or morematerials, including but not limited to, monotungsten carbide (WC),ditungsten carbide (W₂C), macro-crystalline tungsten carbide, cobalt,titanium carbide, tantalum carbide, metal borides, metal oxides, metalnitrides, polycrystalline diamond compact (PDC), thermally stablepolycrystalline diamond (TSP), cubic boron nitride (CBN),polycrystalline cubic boron nitride (PCBN), tungsten, iron, nickel,titanium and boron carbide.

In an example embodiment, cutting inserts 252 are fabricated fromsintered tungsten carbide. To assure adequate wear resistance of thecutting inserts 252, the cobalt content of the cutting inserts 252 isless than 20 weight percent.

Bearing elements including, but not limited to, an outer ball race 270and an inner ball race 271 may be positioned within the roller conemodel 200 for subsequent insertion of a bearing. Retaining impressions273, 274 may also be formed in the roller cone model 200 duringfabrication of the model 200. Retaining impressions 273, 274 may bedesigned to retain bearing elements including, but not limited to,tubular bushing inserts, resilient energizer rings and pilot pins. Theroller cone model 200 may be used to fabricate a roller cone mold 210(shown in FIG. 6C).

Referring to FIG. 6B, a perspective view of an exemplary mold assembly206 is illustrated. The roller cone model 200 may be constructed frommaterial such as wax, polymer or combinations thereof. A down sprue 202and sprue cup 204 are secured to the roller cone model 200 to create amold assembly 206. The down sprue 202 and sprue cup 204 are constructedfrom material such as wax, polymer or combinations thereof. The downsprue 202 and sprue cup 204 may be constructed from the same material asthe roller cone model 200 or a dissimilar material. Mold material may beapplied to the external periphery of the mold assembly 206 by submergingthe mold assembly 206 in a flask 250 containing mold material. The moldmaterial may comprise ceramic, sand, graphite, clay, plastic, rubber,wax and/or other refractory materials known in the art for fabricatingdownhole tool molds.

In an example embodiment, the mold material is a ceramic slurrycomprising zirconium silicate (ZrSiO4), water and alcohol. The moldassembly 206 is submerged in the mold material a plurality of times.Prior to each submersion, the previous layer of mold material may bepermitted to cure or substantially harden. Mold material may be cured orsubstantially hardened at ambient temperature or at an increasedtemperature. Other mold material such as sand may be added on top of theceramic slurry layer to improve mold assembly 206 strength for handling.

In an example embodiment, at least one first internal layer of ceramicslurry mold material is applied to the external periphery of the rollercone model 200 to assure a proper surface finish of the roller cone mold210 (shown in FIG. 6C). Additional layers of mold material including,but not limited to, ceramic, sand, graphite, clay, plastic, rubber, waxor refractory material may be applied on top of at least one layer ofceramic slurry mold material to finish and strengthen the mold 210 forhandling.

Mold material may be applied to the external periphery of the moldassembly 206 in several ways, including but not limited to, sprayingmold material on the external periphery of the mold assembly 206,placing the mold assembly 206 into a container and pouring mold materialon the external periphery of the mold assembly 206, applying moldmaterial in paste form to the external periphery of the mold assembly206 or blowing mold material on the external periphery of the moldassembly 206.

After a sufficient quantity of mold material (e.g. ½″ layer of moldmaterial) is applied to the mold assembly 206, the mold material andmold assembly 206 is heated to a temperature sufficient to cure orsubstantially harden the mold material and melt, burn and/or vaporizethe mold assembly 206 from within the mold 210 (shown in FIG. 6C). Themold assembly 206 may also be dissolved with a dissolving composition.Cutting inserts 252 and bearing elements including the outer ball race270 and the inner ball race 271 (shown in FIG. 6A) are retained withinthe mold 210 after the mold assembly 206 (shown in FIG. 6B) is melted,burned, vaporized or dissolved from within the mold 210 (shown in FIG.6C).

Referring to FIG. 6C, a cross sectional view of an exemplary roller conemold 210 is illustrated. After the mold assembly 206 (shown in FIG. 6B)is melted, burned, vaporized or dissolved from within the mold 210, theremaining structure includes the mold 210 a down sprue 202′ and spruecup 204′ formed from mold material. A composite matrix material inpowder form may be placed within the sprue cup 202′, the down sprue 204′and the mold 210. The composite matrix material is heated to atemperature sufficient to melt the composite matrix material. Thecomposite matrix material flows down the down sprue 202′ and into themold 210. The composite matrix material hardens within the mold 210 toform a metallurgical bond with the cutting inserts 252 and bearingelements including the outer ball race 270 and the inner ball race 271(shown in FIG. 6A) retained within the mold 210. The mold 210 may beremoved from the cast hardened composite matrix material to produce afinished roller cone 200′ including cutting inserts 252 (shown in FIG.6E) and bearing elements (shown in FIG. 6A).

The composite matrix material comprises two or more constituents thatform a single miscible liquid mixture of all constituents at or abovethe eutectic temperature of the composite matrix material. The compositematrix material may comprise two or more constituents including, but notlimited to, monotungsten carbide (WC), ditungsten carbide (W₂C), cobalt,tungsten, iron, nickel, titanium and boron carbide. In an exampleembodiment, the composite matrix material comprises monotungsten carbide(WC) and cobalt.

In an example embodiment, a particulate material 260 is selectivelydispersed within the mold 210. The composite matrix material isinfiltration cast within the mold 210 containing the selectivelydispersed particulate material 260 to increase the strength, wearresistance or toughness of select surfaces of the finished roller cone200′ (shown in FIG. 6E). Particulate material 260 may comprise one ormore constituents, including but not limited to, monotungsten carbide(WC), ditungsten carbide (W₂C), macro-crystalline tungsten carbide,cobalt, titanium carbide, tantalum carbide, metal borides, metal oxides,metal nitrides, polycrystalline diamond compact (PDC), thermally stablepolycrystalline diamond (TSP), cubic boron nitride (CBN),polycrystalline cubic boron nitride (PCBN), tungsten, iron, nickel,titanium and boron carbide.

The composite matrix material may be cast within the mold 210 undervacuum conditions in a vacuum furnace. The composite matrix material mayalso be cast within the mold 210 in the presence of a protectiveatmosphere such as an inert atmosphere including argon or a reducingatmosphere including hydrogen, methane and/or other gaseous hydrocarbonsthat scavenge oxygen. It is also contemplated that the composite matrixmaterial may be cast within the mold 210 in air after applying aprotective coating over the composite matrix material. The protectivecoating may comprise silicon oxide, boron oxide, calcium oxide or zincoxide.

Referring to FIG. 6D, a cross sectional view of another exampleembodiment of a roller cone mold 210 is illustrated. The roller conemold 210 is manufactured by applying mold material to the externalperiphery of a roller cone model 200 and at least a portion of cuttinginserts 252 positioned therein (shown in FIG. 6B). The roller model 200(shown in FIG. 6B) is eliminated from within the roller cone mold 210 bymelting, burning, vaporizing or dissolving the model 200. Cuttinginserts 252 are retained within the mold 210 after the model is melted,burned, vaporized or dissolved from within the mold 210. It is alsocontemplated that cutting inserts 252 may be positioned directly withinthe mold 210 before the mold 210 fully cures and after the roller conemodel 200 (shown in FIG. 6B) is melted, burned vaporized or dissolved.

Composite matrix material 222 may be cast directly into the roller conemold 210 and about a portion of cutting inserts 252 by pouring thecomposite matrix material in molten or liquid form directly into theroller cone mold 210. The composite matrix material 222 is poureddirectly into the mold 210 in molten or liquid form through a container240 such as a crucible or ladle that will not degrade during casting.The composite matrix material hardens within the mold 410 to form ametallurgical bond with cutting inserts 252 retained within the mold210. The mold 210 may be removed from the cast hardened composite matrixmaterial to produce a finished roller cone 200′ (shown in FIG. 6E). Thecutting inserts 252 retain their mechanical properties within thefinished roller cone 200′ (shown in FIG. 6E).

The composite matrix material 222 comprises two or more constituentsthat form a single miscible liquid mixture of all constituents at orabove the eutectic temperature of the composite matrix material 222. Thecomposite matrix material 222 may comprise two or more constituentsincluding, but not limited to, monotungsten carbide (WC), ditungstencarbide (W₂C), cobalt, tungsten, iron, nickel, titanium and boroncarbide. In an example embodiment, the composite matrix material 222comprises monotungsten carbide (WC) and cobalt.

The composite matrix material 222 may be cast within the mold 210 undervacuum conditions in a vacuum furnace. The composite matrix material 222may also be cast within the mold 210 in the presence of a protectiveatmosphere such as an inert atmosphere including argon or a reducingatmosphere including hydrogen, methane and/or other gaseous hydrocarbonsthat scavenge oxygen. It is also contemplated that the composite matrixmaterial 222 may be cast within the mold 210 in air after applying aprotective coating over the composite matrix material 222. Theprotective coating may comprise silicon oxide, boron oxide, calciumoxide or zinc oxide.

In an example embodiment, a particulate material 260 is selectivelydispersed within the mold 210. The composite matrix material 222 isinfiltration cast within the mold 210 containing the selectivelydispersed particulate material 260 to increase the strength, wearresistance or toughness of select surfaces of the finished roller cone200′ (shown in FIG. 6E). Particulate material 260 may comprise one ormore constituents, including but not limited to, monotungsten carbide(WC), ditungsten carbide (W₂C), macro-crystalline tungsten carbide,cobalt, titanium carbide, tantalum carbide, metal borides, metal oxides,metal nitrides, polycrystalline diamond compact (PDC), thermally stablepolycrystalline diamond (TSP), cubic boron nitride (CBN),polycrystalline cubic boron nitride (PCBN), tungsten, iron, nickel,titanium and boron carbide.

The particulate material 260 may be evenly dispersed throughout the mold210 before the composite matrix material 260 is infiltration cast withinthe mold 210. More than one bed of particulate material 260 comprisingone or more dissimilar constituents may be dispersed throughout the mold210 before the composite matrix material 260 is infiltration cast withinthe mold 210. The strength, wear resistance or toughness of selectsurfaces of the finished roller cone 200′ (shown in FIG. 6E) may beoptimized by varying the composition and location of the particulatematerial 260 within the mold 210.

In an example embodiment, the particulate material 260 comprisestungsten carbide and cobalt. The cobalt content of the particulatematerial 260 is less than 20 weight percent to assure sufficient wearresistance of select surfaces of the finished roller cone 200′ (shown inFIG. 6E).

FIGS. 8A through 8D illustrate microstructures formed from casting acomposite matrix material in accordance with the present disclosure. Acomposite matrix material comprising monotungsten carbide (WC) andcobalt was cast within a container. The casting was performed undervacuum conditions in a vacuum furnace to reduce the possibility of airpockets and protect the composite matrix material from oxidation.

Referring to FIG. 8A, a composite matrix material comprising amonotungsten carbide content of 25 atomic percent and a cobalt contentof 75 atomic percent was cast in aluminum oxide (Al₂O₃) and zirconiumoxide (ZrO₂) crucibles including an external layer of painted zirconiumsilicate (ZrSiO4). The composite matrix material formed an ingot afterbeing cast into the crucibles at temperatures ranging from 1357° C. to1500° C. with hold times between 15 min and 120 min. The resultingmicrostructure includes a continuous phase 600 of cobalt and aselectively dispersed particulate phase 602 of evenly dispersedmonotungsten carbide particles.

Referring to FIG. 8B, a composite matrix material comprising amonotungsten carbide content of 25 atomic percent and a cobalt contentof 75 atomic percent was infiltration cast into a bed of monotungstencarbide (WC) (Macroline®, spherical and crushed cast) in aluminum oxide(Al₂O₃) and zirconium oxide (ZrO₂) crucibles including an external layerof painted zirconium silicate (ZrSiO4). The composite matrix materialwas infiltration cast at a temperature of 1500° C. with a 120 min holdtime to enable adequate infiltration. The resulting microstructureincludes a continuous phase 600 of cobalt with a selectively dispersedparticulate phase 602 of monotungsten carbide particles and asub-stoichiometric phase 604. The sub-stoichiometric phase 604 ischaracterized by the following chemical formula: M_(x)C, where M iscobalt or tungsten (W), C is carbide and x is a number between 1 and 6

Referring to FIG. 8C, a composite matrix material comprising amonotungsten carbide content of 25 atomic percent and a cobalt contentof 75 atomic percent was infiltration cast into a bed ofmacro-crystalline tungsten carbide in aluminum oxide (Al₂O₃) andzirconium oxide (ZrO₂) crucibles including an external layer of paintedzirconium silicate (ZrSiO4). The composite matrix material wasinfiltration cast at a temperature of 1500° C. with a 120 min hold timeto enable adequate infiltration. The resulting microstructure includes acontinuous phase 600 of cobalt, a selectively dispersed particulatephase 602 of macro-crystalline tungsten carbide particles and a eutecticparticulate phase 604 comprising a eutectic composition of cobalt andmonotungsten carbide particles.

Referring to FIG. 8D, a composite matrix material comprising amonotungsten carbide content of 25 atomic percent and a cobalt contentof 75 atomic percent was infiltration cast into a bed ofmacro-crystalline tungsten carbide in aluminum oxide (Al₂O₃) andzirconium oxide (ZrO₂) crucibles including an external layer of paintedzirconium silicate (ZrSiO4). The composite matrix material wasinfiltration cast at a temperature of 1500° C. with a 120 min hold timeto enable adequate infiltration. The resulting microstructure includes acontinuous phase 600 of cobalt and a selectively dispersed particulatephase 602 of macro-crystalline tungsten carbide particles.

The methods, systems and compositions herein disclosed for manufacturingdownhole tools and tool parts are not limited to manufacturing rollercones and fixed cutter bit bodies. The methods, systems and compositionsherein disclosed can be used to manufacture downhole tool parts andtools such as casing bits, reamers, bi-center rotary drill bits, reamerwings, down-hole milling tools, bi-center drill bits, well completionequipment and/or other drilling tools known in the art for drillingsubterranean material and/or completing subterranean wells.

Example embodiments have been described hereinabove regarding improvedmethods, systems and compositions for manufacturing downhole tools.Various modifications to and departures from the disclosed exampleembodiments will occur to those having skill in the art. The subjectmatter that is intended to be within the spirit of this disclosure isset forth in the following claims.

What is claimed is:
 1. A downhole tool part for drilling subterraneanmaterial, the downhole tool part comprising: a composite matrixcomposition comprising a constituent material and a carbide material,the composite matrix composition further comprising: a continuous phaseof the constituent material; and a eutectic particulate phase formedfrom a eutectic composition of the constituent material and the carbidematerial; and a particulate material dispersed throughout the compositematrix composition of the downhole tool part, the particulate materialcomprising at least one material selected from the group consisting ofpolycrystalline diamond compact (PDC), thermally stable polycrystallinediamond (TSP), cubic boron nitride (CBN), and polycrystalline cubicboron nitride (PCBN).
 2. The downhole tool part of claim 1, wherein theconstituent material and the carbide material are selected from thegroup consisting of: monotungsten carbide (WC), ditungsten carbide(W₂C), cobalt, tungsten, iron, nickel, titanium, and boron carbide. 3.The downhole tool part of claim 1, wherein the carbide materialcomprises tungsten carbide and the constituent material comprisescobalt.
 4. The downhole tool part of claim 3, wherein the compositematrix composition comprises about 25 atomic percent tungsten carbideand about 75 atomic percent cobalt.
 5. The downhole tool part of claim3, wherein the composite matrix composition comprises equal to orgreater than about 70 atomic percent cobalt.
 6. The downhole tool partof claim 1, wherein the downhole tool part is a bit body.
 7. Thedownhole tool part of claim 1, wherein the downhole tool part is aroller cone.
 8. The downhole tool part of claim 1, further comprising abit body element comprising at least one material selected from thegroup consisting of: monotungsten carbide (WC), ditungsten carbide(W₂C), macro-crystalline tungsten carbide, cobalt, titanium carbide,tantalum carbide, metal borides, metal oxides, metal nitrides,polycrystalline diamond compact (PDC), thermally stable polycrystallinediamond (TSP), cubic boron nitride (CBN), polycrystalline cubic boronnitride (PCBN), tungsten, iron, nickel, titanium, and boron carbide.